中国聚变工程实验堆等离子体螺旋波阻尼系数的研究

Helicon wave damping coefficient of Chinese fusion engineering testing reactor plasma

中国聚变工程实验堆(CFETR)是我国自主设计和研制的新一代磁约束聚变装置.基于快波的色散关系,通过理论分析和数值求解等离子体色散函数Z(ξ),获得了螺旋波(快磁声波)与等离子体相互作用波阻尼因子G与等离子体参数和波频率等的关系.研究结果表明:在CFETR等离子体放电参数下,螺旋波能够产生显著的离轴波功率沉积和波驱动电流,波与等离子体相互作用的主要物理机制是电子朗道阻尼.此外,螺旋波阻尼系数与发射波(谱)的平行折射率和等离子体参数密切相关,但总是随着波频率增加而变大.对CFETR装置混合运行模式的GENRAY/CQL3D模拟研究结果表明,800 MHz的螺旋波能够在r≈0.5a处产生显著的波功率沉积和波驱动电流,驱动电流的效率约为50 kA/MW.

The Chinese fusion engineering testing reactor(CFETR), complementing the ITER facility, is aimed at building up the science and technology base for the prototype of fusion power plant(PFPP). Based on the dispersion relation of fast wave, the analysis of the plasma dispersion function Z(ξ) is performed and a numerical solution of Z(ξ)is obtained. As the consequence, the dependence of helicon wave damping factor G on the plasma parameters and that on the wave properties are both achieved. The results show that an off-axis power deposition of the wave along the device radius can be achieved under the condition of plasma discharge on CFETR tokamak. Moreover, by calculating the ratio of the electron Alfven damping in the ion cyclotron range of frequencies to the electron Landau damping, we find that the electron Alfven damping is dominant at lower wave frequencies. With the wave frequency increasing, the electron Alfven damping remains unchanged while the Landau damping increases rapidly. With the discharge parameters of CTETR hybrid mode, the electron Landau damping proves to be dominant. Moreover, the off-axis power deposition and current drive profiles are produced. It is shown that the helicon wave damping factor increases with wave frequency increasing and it is closely related to the parallel refractive index of the injected wave spectrum, the plasma density, and plasma temperature. Significant off-axis power deposition and current drive are shown in CTETR hybrid mode operation, and the current drive efficiency reaches 50 kA/MW for helicon wave with a frequency of 800 MHz. Numerical simulation performed on the GENRAY/CQL3 d shows a good consistence with the experimental results.